Papillomaviruses are small DNA tumor viruses, a subset of which are associated with human cancers. HPV-16 represents the prototype oncogenic mucosotropic HPV owing to its frequent association with oral, cervical, penile and anal cancers. In the Lambert laboratory, we study the oncogenic potential of HPV-16 and its life cycle. Over the current funding period we have elucidated the roles of E6 and E7 in cancer using transgenic mouse models, and have established in our hands the tools for studying the role of individual viral genes in the viral life cycle. These latter studies led to the demonstration of E7's requirement in the productive stage of the viral life cycle in which the virus reprograms terminally differentiated epithelial cells to support viral DNA amplification. We have likewise initiated studies on three other viral genes, E6, E5, and E1; each of which possess biological properties that are suggestive of their roles in the propagation of virus in its natural host. In the process of studying E1, we discovered the ability of papillomavirus genomes to replicate in mammalian cells as well as in yeast independently of E1. The aims of this Project are focused on further understanding the role of E7, E6, and E5 in the viral life cycle, and to distinguish the roles of E1-dependent versus E1-independent replication in the viral life cycle. These studies will continue to make use of the HPV-16 virus as a prototype mucosotropic virus for study in the laboratory.